1. Field of the Invention
The present invention relates to a device and a method used in a wireless communication system, and more particularly, to a device and a method of handling mobility management.
2. Description of the Prior Art
A long-term evolution (LTE) system provides high data rate, low latency, packet optimization, and improved system capacity and improved coverage. The LTE system is evolved continuously to increase peak data rate and throughput by using advanced techniques, such as carrier aggregation (CA), dual connectivity, licensed-assisted access, etc. In the LTE system, a radio access network known as an evolved universal terrestrial radio access network (E-UTRAN) includes at least one evolved Node-B (eNB) for communicating with at least one user equipment (UE), and for communicating with a core network. The core network may include a mobility management and a Quality of Service (QoS) control of the at least one UE.
According to operations defined for the LTE system, a UE always performs an attach procedure to a mobility management entity (MME), when the UE moves from a first network to a second network and has no Packet Data Network (PDN) connection in the first network. However, the attach procedure causes a great amount of overheads including extra messages exchanged between the MME and the UE. In other words, cost of mobility management is too high to improve throughput of the LTE system. Therefore, reduction of the overheads for handling mobility management is an important problem to be solved.